This invention relates to keyboard systems and more particularly to pushbutton keyboard systems for use in electronic pocket calculators, telephones or the like.
In conventional pocket calculators, data (e.g., numbers and arithmetic operations) are usually entered by depressing specified keys which close simple single pole, single-throw (SPST) momentary switches. The physical arrangement of the keys on the keyboard is generally an X-Y matrix (i.e., an array of perpendicular columns and rows). Upon depressing a selected key, an unique signal is generated. For example, the columns in the array of keys may be designated KN, KO, KP and KQ and the rows of keys may be designated D1, D2,. . . D11 so that, for example, upon depressing the key in column KN and in row D1, a signal corresponding to the numeral 1 is supplied to the calculator.
While the physical arangement of many known prior art keyboards may be arranged in an orderly X-Y matrix, the electrical conductor paths of the keyboard generally have not followed this orderly arrangement. Oftentimes, the type of switches used in keyboards has required there to be several conductive paths to each switch thus necessitating that relatively complicated and complex conductor patterns be imprinted on a printed circuit board or the like. In other known prior art keyboards, a generally rectangular X-Y conductor matrix has been employed, but the conductors crossed one another in a grid pattern and exited the keyboard both at the top and at one side thereof thus requiring additional connector or umbilical wires to be attached to the conductors before the keyboard could be connected to a motherboard or electronic logic components. The connection of these connector wires to the conductors is time consuming and expensive.
In earlier keyboard systems generally similar to the present invention, flat metal strips of generally rectangular cross-section were used as conductors. These strips were required to be specially fabricated and entailed additional fabrication costs.
Reference may be made to the following coassigned U.S. patents which are believed to be representative of the present keyboard state of the art: 3,684,842, 3,806,673, and 3,808,384.